The thematic move. It's always dangerous for White to take the knight due to the dark squares, although in some cases this is the best move.
25. f1e1  25... e6e5 Not afraid to allow f4-f5. With the rook on h8, Black always has counterchances. 26. f2d2  26... d8c7  27. f4f5 After this, Black has the advantage again.